Abta spokeswoman Gillian Edwards said thousands have already flown back to the UK or scrapped plans to visit Tunisia following the Sousse beach massacre a fortnight ago.

She said: “We estimate there are around 3,000 British tourists out in Tunisia at the moment - that is dramatically lower than you would normally expect for this time of year because of the incident.

“Normally it would be around 20,000 to 25,000 British holidaymakers out there.

“Our advice to people who are out there is to contact their travel company to find out about their options and confirm their flights home. The tour operators are aiming to get everyone home by the end of Sunday.

“In Tunisia around 90% of the holidays are package holidays, the majority of people are travelling with a tour operator. Those people who have travelled out there independently, they will need to contact their airline to find out what their options are.”

Ms Edwards said it is very unusual for the Foreign Office to take such a drastic step, and she thought the vast majority of British tourists will heed the advice and head home, but a “small minority” who know the country very well might stay.

She said: “For the Foreign Office to issue this kind of travel ban is highly unusual, particularly for a very popular tourist destination.

“The Foreign Office would have taken a huge amount of information into consideration that has come to light since the attacks, they won’t make this decision lightly, so it is a very unusual situation to do this.”

Britons are among the biggest customers of Tunisia’s tourist industry, and the travel warning will seriously damage trade, she warned.

She said: “I think in the short term it is going to have a very serious impact on tourism. British holidaymakers are one of the main groups of holidaymakers to travel out to Tunisia.”